Kristin Scott Thomas has been a Euro arthouse queen, has been booked up by Hollywood's elderly leading men, and now her career is entering its most exciting phase yet

Kristin Scott Thomas and Ralph Fiennes pose during the presentation of Cromophobia in Madrid.

PHOTO: EPA

For someone who wouldn't drop her guard if her life depended on it, Kristin Scott Thomas is fun to be around. The 47-year-old actress, raised in Cornwall but resident in Paris since she was 19, sits at a corner table in the restaurant at London's Claridge's hotel, wearing a white smock with chunky brown and turquoise beads. She's playfully combative, but she can also be suddenly, shockingly serious. When I ask if she thinks her new film, The Walker, is any good, she looks straight at me and says: "I haven't seen it. Do you want to carry on now I've told you that?" I mull it over and decide, on balance, not to storm out. "I can tell you about shooting it," she offers helpfully. Then she gets very defensive: "There's not much point me talking about what the film is anyway, because I have nothing to do with that. I'm just the raw material." And finally, a dash of ebullience: "What did you think of the film? People have told me it's fantastic! I'd love to see it. They really should've set up a screening for me." Phew. And - relax.

Her sources are not just flattering her: The Walker, written and directed by Paul Schrader, is something to be proud of. Hers is a supporting part - the picture really belongs to Woody Harrelson as a gay "walker," or escort, to politicians' wives in Washington DC. But, as Lynn Lockner, one of these pet socialites who draws him deeper into her life when her lover is murdered, Scott Thomas captures the sadness and sense of waste in a vibrant woman worn down by years of being ignored by her senator husband. "Lynn is frustrated that she has become an accessory," she explains. "She wants to be a normal person and be loved, and get back what she sacrificed for her husband's career."

Scott Thomas gives the impression of needing to work with people who are her equals in toughness as well as talent; if this is so, she met her match in the famously gruff Schrader. On the day of her big scene - a showdown with Harrelson in a hotel room - she asked Schrader how he planned to shoot it. "He said, 'Well, we'll shoot Woody, then we'll turn around and do the complementary.' I said, 'That's me, is it? The complementary?'" She turns livid at the memory. "I had to stay concentrated, but I was fuming." Still, the scene went well, and the next day she asked Schrader for instructions on what to do during one of Harrelson's scenes. "Just be attentive and attractive," shrugged the director. "That's when I realized he was teasing," she laughs. "As he was walking away, he caught his head on the scrim, and I called out, 'Serves you bloody right!'" She adores that story.

"What I loved about Paul's script," she explains, "was that these people are lying all the time. That's what drew me to it - the idea of that double life, the weight of secrets. Lynn has to keep going whether she's terrified or heartbroken; she has to maintain her facade and hold things together. She's acting the whole time."

No one who is familiar with recent developments in Scott Thomas's life can possibly hear this talk of secrets and double lives without interpreting it as some kind of veiled confession. I'm sure she's not playing peek-a-boo here - it wouldn't be her style to drop hints about her personal life when she works so hard to purge her conversation of intimate details. And journalists know better than to ask. If there's one thing you learn from perusing nearly 20 years' worth of interviews with her, it's that you don't enquire about anything other than her work unless you want a cold response.